1. Field of the Invention
This invention relates to spatial light modulators, more particularly to micromechanical spatial light modulators.
2. Background of the Invention
Spatial light modulators in some embodiments consist of arrays of individually addressed elements. Examples of these type of modulators include liquid crystal devices (LCD), digital micromirror devices (DMD.TM.), and actuated mirror devices (AMA.TM.). The DMD and the AMA are micromechanical devices, meaning that they have miniaturized parts that move when the elements are activated.
Micromechanical modulators have the advantage of being a product of manufacturing processes that are compatible with most semiconductor processing steps. They have a further advantage that they can be manufactured on an extremely small scale. Their moving parts are very simple, typically a flap that deflects either in one of two directions, or in one direction. They are activated by electrostatic or piezoelectric forces, for example, that cause the flap to deflect. When the flap deflects, the reflection angle of light that impinges on the surface of the flap changes.
These modulators can be operated in an analog fashion or digitally. In the analog mode, they typically achieve a range of angles of deflection based upon the forces between the flap and the addressing circuitry. To operate digitally, they typically deflect to a stable position, more often than not coming to rest against some type of landing stop.
With the move to digital imaging in areas such as printing and displays, the desirability for a digitally operated spatial light modulator has increased. However, in digital operation, while more stable than analog, the repeated contact between the deflected element and its landing stops causes the element to stick to the landing stops. Once stuck, these elements cause bright or dark spots on the final image.
Therefore, a solution is needed that prevents or mitigates the problems caused by the sticking of these elements to their landing stops.